Compensation for phase variations



Dec. 24, 1929. 1,740,491

H. A. APFEL COMPENSAIION FOR PHASE VARIATIONS Filed Sept. 23, 1927 2Sheets-Sheet l Kadi? 27mm;-

L mitter Halm Pfad. I

29 Flaum A TTORNEY 1929- H. A. AFFEL.

COMPENSATION FR PHASE VARIATIONS Filed Sept. 23, 1927 2 Sheets-Shee i?eaStep- I7anJmitter Darin forfi'Pgue/Ilg aj' 70000 cycles IN V EN TOR.Ajjfe!) ATTORNEY Patented Dem 24, 1929 fects of other inte'rference.frequency broadcasting system, therefore, 1t

UNITED STATES PATENT OFFICE EERMA.N A. APFEL, DIE RIDGEWOOD, NEW JERSEY,ASSIGNOR T0 AMERICAN TELE- J?EONE .AND TELEGRAIE COMPA.NY CORPORATIONO]? NEW YORK GOIMI]?ENSATION FR PHASE VARIATIONS Applieation filedSeptember 23, 1927. Sexial N0. 221,564.

This invention relates to arrangements and methods by which Phasevariati0ns on line circuiizs anal more particularly on open wire lines,may be counteracted 01 equalized.

While it may be important to counteiat 01' equalize Phase variations online circuitsnnder various circumstances, it is more particu.

larly important where the line Circuits are employed for transmitting ailot 0x control frequency f01 a chain broadnasting system. It has beenproposed, f01 example, that bioadcasting be accomplished from a, numberof stations employing a common frequency, and that the difl'erentstations be kept in synchronism by means 0f a control frequencytransmitted over wires. With such an arrangement, relatively smallvari&tions in the hase 0f the 10W frequency currents transmitted overthe line would, by virtue of the frequency m-ultiplication employed ateach broadcasting station, be greatly magnified in stepping-up thecontrol frequency to-a radio frequency. F01 a listener so located as t0receive approximately equal field strength from two broadcastingstations operating on the same wave length, the variations in the phaseof the radio frequency currents at the tw0 stations would produce 510Wfading ef- For a common is highly desirable to eliminate variations inthe phase 01? the control frequency transmitted over the wire circuits.

In ancordance with the present invention, it is proposed to accomplishthis result by making phase ad) ustments in solne adjustable element ofthe circuit at the broadcasting station t0 compensate f0r any changes inphase 0f the 'control frequency as 1ts a1- rives at the station. As itis imprantical to make direct observations of the changes in phase whichoccur, it is desirable to make compensating adjustments in accordancewith sonne other characteristic of the control frequency wh ich varieswith the hase. In cab1e circuits the principal change is a. change 0fresiStance corresponding to varmtions in thetemperature to which thecabl is subjecbed. 'Iherefore, the change in phase 0f the arrivingcurrent Will bear a definit e relation to the change in the resistance0f the c1rcu1t. It has been heretofore proposed to compensate .forchanges in hase of the arriving currents in a cable circuit by makingcurrent is concerned. In open wire circuits thg most eflecti ve factor,from the standpo mt of causing change in phase, is the variat1on in thecapacity 0f the insulators as the weather conditions vary from wet todry 'Ihis change in hase shift is accompanied by a change 0f"attenuation resulting fron1 changes of the insulator capacity.

In general, a definite relation exist-s in opeii vqire circuits betweenthe change in attenuat1on which occurs with varying weather C011-ditions, and thechange in phase shift of the currents transrnitted overthe line. In accordance with this invention, it is proposed 130 takeadvantage of this fact by making compensating phase adjustments inaccordance with hoted changes in the attenuation of the currents incoming from the open wire line at the broadcasting station. ing adjustmentsmay be made either manually 01' automatically.

'Ihe invention ma now be m0re fully understood :hom the fo lowingdetailed description, when read in connection with the accompanyingdrnwings, in which iFrigure 1 shows in schematic form a, circuitnrrangemenf for carrying outthe invention; Fig. 1 shows in somewhat mredetail the natur'e of the phase controlling arrangements employed; Figs. 2 and 3 sI1ow modified forms of. circuit arrangements for carryingout the These compensatprinciples of the invention; and Fig. 4 is a mtion and the phase shift in the case of a 104 some definite relation tothe ch'ange in the attenuation of the open Wire circuit. Inasmuch,however, as the change in tl1e attenuation is due largely to theconditions of insula, tion 0f the circuit, it is evident that therelation between phase shift and change in attenuation in a given casewill depend upon the design of the insulator structure employed.

In Fig. 4, the curve w depicts grzxphically the relation between thechange in attenuamil pair for a line construction employing insulatorsof a type commonly employed for telephone purposes. Curve y similarlydepicts the relation in the case of a 165 mil pair under similarinsulating conditions; These cufves, being straight lines, disclose theinteresting fact that for the particular type of insulator hereinvolved; a direct proportionality exists between the change inattenuation and the change in phase shift. This simple relation permitsof a correspondingly simple mechanical connection between thepotentiometer and phase controller which are emloyed in the apparatushereinafter described. Iowever, it must be borne in mind that for othertypes 0f inSulator construction this Clirect linear relation may notexist, and the relation between attenuation and phase shift may be aconstantly varying one. Even though the relation be variable, however,it is still possible to design a potentiometer or amplitude controllerand a phase controllin device which may be so related as to bring a outthe desired phase compensation by a simple manual adjustment.

Referring now t0 Fig. 1, which illustrates a circuit diagr am embodyingthe above principles, X and Y des"ignate enerally two radio broadcastingstations Wh10h are intended to broadcast at the same wave length. Theapparatus at station X comprises an oscillator' O for generating a baseor contro'lling frequency which may be, for exarnple, 5,000 cydes, a,harmonic producet H indicated con ventionally, a, radio transmitter Talso indicated conVentionally, and a transmitting antenna A Thefrequeney generated by the oscillator is applied to the harmonicproducer H to produce the desired harmonic which is intended to beusedas the carrier wave for the radio transmitteh The harmonic producermay be of any known type such, for example, as a distorting vacuum tube.together with a suitable tuned circuit or other selective device forselecting the desixed harmonic. The radio transmitter T, may likewise beof any knoWn type, such as is now commonly employed forbroadcasting.

The frequency generated by the oscillator O is transmitted over the wireline L to the station Y, at which point it may be applied to -theharmonic genera.tor H simil ar in all respects to the harmonicgeizerator H, The

desired harmonic which is to be used for ra-.

dio transmission is then transmitted to thn' radio transmitter T thistransmitter beiilg similar to that shown alt station X. The transmitterin turn is conneeted to the transmitting antenna A By deriving the radiowave ab the stations from the Same fundamental, the two stations willbroadcast at the same wave length. If, however, the Phase relation o fthe frequencies employed by the two stations changes from time to time,as it will due to the v-urying conditions 0f the line L, a, listener aba osition intermediate between the two stat1on5 Will encounterinterference which will be manifested as a waxing and waning of thesignal. It is therefore necessary to maintain the phase relationsconstant in order to avoid such interference.

This may be accomplished by providing a phasecontrol mearis which, asillustrated, comprises a variable condenser 10 shunted across the lineand a variable inductanee comprising coils 11 and 12 in series with theline.

The coils 11 and 12 are mounted as shown in F ig. 1 so as to berotatable With respect to each other, thereby x arying the mutualinductance. By adj usting the coil and the COD- denser, the phase of thearriving wave may be controlled without changing the attenuation =of thecirmiit.

In Order that this adjustment may be made in such a manner as tocompensate for any change in phase which has occurred, an amplitudecontroller, eomprising an adjustable potentiometer 13 is associated withthe line L, as indicated, and a rectifying thermobuple 14, together witha meter 15, is connected in the output of an amPlifier 16 through whichthe control frequenc is supplied to the harmonic producer Thethermocouple 14 enables the meter 15 to record the amplitude of thecontrol frequency incoming from the line L and thereby' bethen bechanged in accordance with the' change in amplitude ind.icated by thechange in the setting of the potentiometer so as to compensate for thechange in hase whih must haire inevitably accompanied the change inattenuation. 1

In order to simplif these adjustments, the c0il 11 of the variab einductance, one plate or s et of plates of the variable condenser 10 andthe movable contact of the potentiometex 13 may be mounted upon'a commonshaft, as indicated in Fig. 1*. The otentiometer is then designed withrespect to the inductauce und condenser so that a change in the settingof the potentiometer, which will coun- Knowing the relation betweenatteract a given change in the attenuation of -the ment of the Phasecontrolling element as will just compensate for the chango in Phasewhich accom anies the change 1 n attenuation. With t is arrangement,whenever the meter 15 shows a departure'from the normal current value,the attendant merely adjusts otentiomeoer 13 to brin the meter readingack to normal. In maing this adjstment the hase controller isautomatically so adjuste as to restore the phase relation b etween the,stations X and, Y.

It will be understood, of course, that the control frequency may, ifdesired, be obtained ftom one of the channels of a carrier telegraphsystem, or it may comprise the sooalled ilot frequency which isfrequently used w1th a carrier system to automatically adjust theattenuation. Or it may, be obtained-from a special source andtransmitted over the transmission line by sandwiehirlg the controllingfrequency in between the chani1els of a carrier system superposed u{)on'the line. The latter arrangement is il trated in Fig. 2. Hera theordinary carrier channels, which may be employed for telephone andtelegraph purposes, are superposed upon the line by transmitting themthrough the filters HF und HF the ordinary voice currents beingtransmitted oven theline throu h the filtels LF and LF.

The oscillator wh ich supplies the control frequency is transmitted tothe harmonio producer llas in Fig. 1, but is transmitted 130 the line Lthrough the filter HE, for transmission to station Y.

At the latter station this frequency, after passing through the filterHF is selected from the various carrier channels by means of a tunedcircuit 20, and after being suitably amplified by an amplifier A istransmitted through the otentiometer 13 und the hase adjuster 10-11 tothe harmonic producer X.

The potei1tiometer andv hase adjuster may be of the same type as ilustrated in Figs. 1

and l, and may be connected together to be adjusted simultaneously inthe manner already described. In order to indicate any chan e from thenormal hase adjustment,

a bri ge connection 21 lea s from the output side of the phase adjuster130 the input of a vacuum tube 22. A second vacuum tube 23 is alsoprovided, and a galvanometer 15 and voltmeter relay 24 are connected inseries between the plates of the tu s 22 and 23. The

- current will flow'through the tubes 22 and 23 act as rectifie? and thepotenti-al applied to the tube 22 s adjustable by means of aPotentiometer 25. The potentibmeter 25 is adjusted so that when theamplilinde (und, of course, the hase) of the eurrent arriving from theline L is normal, no

lvanometer f the ampliease, current 15 and the voltmeter relaY 24. laudeof the current shou d incr Will flow throgh the alvanometer and voll:-meter relay in such a irection as to shift the armature of the voltmeterrela to olose the circuit through the indicator amp 26. If, on the otherhand, the attenuation of the circuit should increase so that theamplitude drops'below normal the rectified current will flow through thevltmeter relay in the opposite direction, causing the armature to olosethe circuit through the other indicating lamp 27. VVhen the circuit ofeither la1hp is closed, the relay 28 will be operated to close thecircuit of an alarm 29. This arrangement not only indicates an abnormalattenuation (and phase) condition, laut it also indicates in whichdireotion the condition has departecl from normal. Therefore, theattendant knows which way he should adjust thdpotentiometerl3 to bringthe amplitude bakzk to normal. Such acljustment, 015 course,automatically restores the phase to normal by ad-* justing the hasecontroller 1011, as already described in connection with Fig. 1.

If desired the acljustment of the potentiometer and phzase controllermay be accomplished automatically, as illustrated in Fig. In this figurethe apparatus at stations X and Y is in general sixnilar to thatillustratod in Fig. 2, except that a part of the current transmitted tothe frequency step-up device H is transmitted through a bridgeconnection 21 to the input of a vacuum tube rectifier 30. A polar relay31 has one wind-' im connected with the lato circuit of the tue 30 undthe other wmding is connected? in circuit with a direct current sourcewhich' may, for example, be the B battery of the tube 30. The currentthrough the right-hand winding of the relay 31 is controllecl bymeans'of .a resistance 32 so that that witha normal cu1rent valueincoming from the line L, the recified current through the left-handWinding of thap'olar relay will be just equal and opposite to thecurrent from the rightolar 1elafy will therefore be in a neutralpos1tion.

I the amplitude of the received current falls below normal, the armatureof the polar relay will be shifted to its right-hand contact, the'rebyclosing the circuit of the relay 32 which connects the power supply to amotor 34 in such a manner as to drive the motor in.one direction. If,one the other band,

hand winding. The zrmature of the the amplitude of the arriving currentincreases, the armature of the polar relay3l tral position and therotation of the motor ceases. Under this condition the amplit-ude of thecurrent incoming from the line L is restored to normal and the phaseadjustor 5 -11 is automatically compensated for the change in phasewhich accompanied the change in attennation, so that the phase is againbrought back to normal.

It will be obvious that the general prin- 10 ciples herein disclosed maybe ernbodied in many other organizations widely different 1"1'0111 thoseillustrated without departing from the spirit of the invention asdefined in the following claims.

What is clain1ed is:

1. The method of compensating, for vari- -ation in the phase shiftresulting fr0m transmission over a transmission line including a phasecontrolling element, which consists in observing the change in amplitudeof the arriving current whicli accompanies such change in phase, andadjusting a phase comtrolling element of the line 1n accordance with theobserved change in amplitude.

2. The method of compensating for variation in the phase shift resultingfrom transmission over a transrnission line including a transmissionelement and a phase controlling element, which consists in observing thevari ation of amplitude of the arriving current which accompanies thechange in phase, adjusting a transmission element of the line to restorethe amplitude to normal, and CO1- respondingly adjnsting a phasecontrolling .element f the line to compensate for the change in phase.

3. The method of compensating for variation in the phase shift resultingfrom transmission over' a transmission line including a transmissionelement and a phase controlling element, Which con sists -isobservingthe variation of amplitude 0f the arriving eurrent whichaccornpanies the change in phase, adjusting a transmission element ofthe line to restore the amplitude to normal, and simultaneouslyadjusting a phase controlling element 2issociated with.the line inaccordance with a prdetermined relation between change in attenuationand change in phase t0 compensate for the phase Variation Whichaccompanied the observed change in amplitude.

4. The method 0f compensating for variation in the phase shift resultingfrom trans mission over a transmission line including a phasecontrolling' element, which consists in observing the change inamplitude of the arriving current which accompanies such change inphase, and automatically adjusting the phase controlling element of theline by an amount corresponding to apredetermined relation between phasechange and the change in attenuation for the line.

5. The method of compensating forvari; ation in the phase shiftresultingfrom transmission over a transmission line inclqpling an amplitudecontrolling element and a phase controlling element, which consists inobserving the change in amplitude which accompanies such change in hase,automatically producing an adjustment of said amplitude con'trollingelement of the line 130 compansate for the observed change in amplitude,and simultaneously producing an automatic adjustment of said phasecontrolling element of the line in a tcordance with a predeterminedrelation between the change in phase and change in amplitude of theline, thereby restoring the hase to normal.

6. A system to compensate f0r variation in phase shift, comprising atransmission line over Which an alternating current may be transmitted,means to indicate a change in the amplitude of the arriving currentWhich corresponds to a change in the phase thereof, and a phase varyingelement associated With the line and adapted to be adjusted inaccordance with the indicated change in amplitude to compensate for thechange in phase.

7. A system to compensate for variation in phase shift, comprising atransmission line over which an alternating current may be transmitted,means to indicate achange in the amplitude of the arriving current whichcorresponds to a change in the hase thereof, an amplitude controllingelement associated with the line and adapted t0 be adjusted to restorethe amplitude to normal, and a phase controlling element also associatedwith the line and adapted to be adjusted by an amount Whose relation tothe adjustment of said am- -plitude controlling element corresponds to apredetermined relation between change in attenuation and change in phasefor the line.

8. A system t0 compensate f0r variation in phase shift, comprising atransmission line over which an alternating current may be transmitted,means to indicate a change in the amplitude of the arriving currentWhich norresponds t0 a change in the phase thereof, an amplit'udecontrolling element associated With the line and adapted t0 be adjustedto restore the amplitude to normal, and an adjustable phase controllingelement associated With the line, said phase controlling element beingso mechanically related to the amplitude controlling element as 't0 besimultaneously adjusted therewith by an amount which is related to theadjust-ment of the amplitude controlling element in accordance with thepredetermined relation between change in attenuation and change in phasefor the line.

9. A System to compensate for variation in phase shift, comprising atransmission line over which an alternating current may be transmitted,means responsive to changes in the amplitude of the arriving currentwhich accompanies a change in phase 0f said current, a phase controllingelement associatecl with the line, and means automatically controlled bysaid responsive means to adjust said hase controlling element by anamount corresponding to a, predetermined relation between phasechange'and the change in attenuation f or the line.

10. A system t0 compensate fo'r variation in hase shift, comprising atransmission line 0ver Which an alternating current may be transrnitted,means responsive to changes in the amplitude of the arriving currentwhich accompanies a change in phase 0f said eurrent, and amplitudecontrolling element associated With the line, a phase controllingelement associated With the line, and means controlled bv saidresponsive means to automaticially ajust said amplitude controllingmeans tc compensate fog the change in amplitude of the arriving currentand t0 simultaneously adjust said'phase controlling means by an amountcorresponding to a predetermined relation between the phase change andthe change in attenuation for the line.

In testimony Whereof, I have signed my name 150 this sgecification this22nd day 0f September, 192

HERMAN A. AFFEL.

